Electrochromic display

ABSTRACT

An electrochromic display is disclosed which comprises an array-side substrate ( 10 ) in which a pixel electrode ( 15 ) and an electrochromic layer ( 30 ) are formed, a color filter-side substrate ( 50 ) in which a counter electrode ( 53 ) and an electrochromic layer ( 54 ) are formed, and an electrolytic layer ( 80 ) injected between the array-side substrate ( 10 ) and the color filter-side substrate ( 50 ). By forming a partition wall ( 23 ) on the periphery of the pixel electrode ( 15 ) and the electrochromic layer ( 30 ), there can be prevented short-circuits between pixel electrodes ( 15 ) and short-circuits between electrochromic layers ( 30 ) between adjacent pixels, thereby realizing an electrochromic display with higher precision.

This application is a continuation of international Application No.PCT/JP2004/010638, filed Jul. 27, 2004, which claims priority toJapanese Application No. JP2003-284037, filed Jul. 31, 2003.

BACKGROUND

1. Field

The present invention relates to an electrochromic display that displaysimages by utilizing an electrochromic phenomenon.

2. Description of the Related Art

Electronic paper is getting more and more attention as a new displaymedium that combines the characteristics as paper, which is no need ofinformation holding energy, can be securely saved, easily read, quicklyreadable and so on, and the characteristics as an electronic displaycapable of rewriting information and so on.

Various types are known as a display principle in the electronic paper.For example, it is a microcapsule type electrophoretic display methodwhere capsules enclosing positively and negatively charged black andwhite particles are moved between electrodes. Further, it is a twistball method where the direction of spherical particles colored in blackand white are controlled. These methods perform display by utilizing aphysical phenomenon.

On the other hand, there is known a method that performs display byutilizing a chemical phenomenon. Among others, one utilizing anelectrochromic phenomenon is known where voltage is applied betweenelectrodes to cause coloring or deletion by oxidation-reductionreaction. This is described in Japanese Patent Laid-Open No. 2002-258327publication, for example.

In the case of an electrochromic display utilizing the electrochromicphenomenon, it is constituted that one substrate on which pixelelectrodes are formed and the other substrate on which counterelectrodes are formed are arranged in a facing manner, and anelectrochromic layer and an electrolytic layer are formed between theboth substrates, in which the electrochromic layer is formed on thepixel electrodes as described in Japanese Patent Laid-Open No.2002-258327 publication.

However, as the number of pixels is increased and the pixels are madesmaller in order to perform display of higher precision, risk of causingproblems increases around pixel electrodes caused by short-circuitbetween adjacent pixel electrodes or short-circuit between theelectrochromic layers on the adjacent pixel electrodes, and it becomesan obstacle in achieving higher precision.

SUMMARY OF THE INVENTION

Consequently, it is an object of the present invention to provide anelectrochromic display capable of performing display of higherprecision.

To solve the above-described problems, the electrochromic display of thepresent invention is characterized by including: a plurality of pixelseach of which is made up of a pixel electrode, a counter electrode, andan electrochromic layer and an electrolytic layer which are formedbetween the pixel electrode and the counter electrode, in whichshort-circuit prevention means is provided around the pixel electrode.

Further, the electrochromic display of the present invention ischaracterized by including: a plurality of pixels each of which is madeup of a pixel electrode, a counter electrode, and an electrochromiclayer and an electrolytic layer which are formed between the pixelelectrode and the counter electrode, in which the electrochromic layeris severally formed on the pixel electrode, and the short-circuitprevention means is provided around the pixel electrode and theelectrochromic layer.

Furthermore, the electrochromic display of the invention ischaracterized in that the short-circuit prevention means is a partitionwall surrounding the periphery of the pixel electrode, and it is alsocharacterized in that the electrochromic layer is formed by usingnano-particle thin film.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional schematic view of a pixel of anelectrochromic display of an embodiment of the present invention.

FIG. 2 shows a plan view of a pixel in an electrochromic display of anembodiment of the present invention.

FIG. 3 shows a circuit diagram of a pixel in an electrochromic displayof an embodiment of the present invention.

FIG. 4 shows a circuit diagram of a pixel in another embodiment.

FIG. 5 shows a circuit diagram of a pixel in another embodiment.

FIG. 6 shows a circuit diagram of a pixel in another embodiment.

FIG. 7 shows a circuit diagram of a pixel in another embodiment.

FIG. 8 shows a circuit diagram of a pixel in another embodiment.

DETAILED DESCRIPTION

In the following, description will be made for embodiments to implementthe present invention based on the drawings. The embodiments show anelectrochromic display of about 8 inches to 10 inches and having a pixelpitch of 80 to 100 μm. FIG. 1 shows the cross-sectional schematic viewof a pixel in an electrochromic display in this embodiment, FIG. 2 showsthe plan view of the pixel, and FIG. 3 is a view schematically showingthe circuit diagram of the pixel. Note that FIG. 1 and FIG. 2 hasdifferent size, shape and the like of each constituent element.

The electrochromic display is constituted by an array-side substrate 10,a color filter-side substrate 50, and an electrolytic layer 80sandwiched between the both substrates.

In the array-side substrate 10, a plurality of gate wires 12 and aplurality of source wires 13 are wired in a matrix state on a glasssubstrate 11. A region surrounded by the gate wires 12 and the sourcewires 13 corresponds to one pixel. A switching TFT 14, a pixel electrode15 connected to the TFT 14, and an electrochromic layer 30 stacked onthe pixel electrode 15 are formed on each pixel. It is preferable thatthe thickness of the electrochromic layer 30 be about 3 to 10 μm, and 3to 4 μm more preferably.

A plurality of the gate wires 12 are formed on the glass substrate 11 bystacking Al and Mo. Further, the gate electrode 16 of the TFT 14 issimultaneously formed when forming the gate wires 12 (not shown in FIG.1). The gate electrode 16 has a size having about 65% of one pixel area,as shown in FIG. 2, and its shape is in an oblong rectangular shapeapproximately similar to the shape of the pixel. It is preferable thatthe switching TFT 14 be capable of flowing as large current as possiblewhen it is turned to ON state for the purpose of performingoxidation-reduction reaction. Therefore, the gate electrode 16 is formedas large as possible.

A gate insulation film 17 made of SiN_(x) is stacked on the glasssubstrate 11, and the gate insulation film 17 covers the gate wires 12and the gate electrode 16. An amorphous silicon (hereinafter, referredto as a-Si) layer is stacked on the gate insulation film 17, and only apart of the layer that falls in the semiconductor layer 18 of the TFT 14is left by a photolithography method (shown in a broken line in FIG. 2).At this point, the semiconductor layer 18 is in a shape covering a majorpart of the gate electrode 16.

A metal layer where Al and Mo are stacked is formed on the gateinsulation film 17 and the semiconductor layer 18, the metal layer ispatterned by the photolithography method to form the source wires 13,the source electrode 19 and the drain electrodes 20 of the TFT 14. Atthis point, the source wires 13 are provided orthogonal to the gatewires 12, and the source electrodes 19 are protruded from the sourcewires 13 at an area near the crossing portion with the gate wire 12.

The periphery of the source electrode 19 is in a shape taken along theperiphery of the gate electrode 16 and also in a shape having U-shapedconcave portions extending along the source wires 13, and it is in ashape having two concave portions in FIG. 2. The drain electrode 20 isin a shape having thin and long rod-shaped convex portions that arelocated between the U-shaped concave portions of the source electrode13, and has two convex portions so as to correspond to the concaveportions of the source electrode 19.

It is preferable that the switching TFT 14 be capable of flowing aslarge current as possible when it is turned to ON state for the purposeof performing oxidation-reduction reaction. Particularly, the TFT 14using a-Si in the semiconductor layer 18 has difficulty of allowingcurrent to flow therein comparing to a TFT using polysilicon despiteadvantages such as easiness of manufacturing comparing to the TFT usingpolysilicon, so it is necessary to make the TFT 14 as large as possible.Although a channel length may be shorter and a channel width may bewider in order to allow current to flow more smoothly, making the TFT 14as large as possible to widen the channel width is more effectivebecause there is a limitation on manufacturing engineering in shorteningthe channel length. The size of TFT may be no less than half the area ofone pixel region, more preferably it may be no less than 60% of thearea.

Consequently, the shapes of the source electrode 19 and the drainelectrode 20 are devised to allow current to flow as much as possiblebetween source/drain when the TFT 14 becomes ON state. Specifically, thegate electrode 16 of the TFT 14 is formed in an oblong rectangular shapecorresponding to the shape of the pixel to make the source electrode 19and the drain electrode 20 long, and the channel width can be wider in alimited space. Further, by providing the U-shaped concave portions inthe source electrode 19 and arranging the drain electrode 20 between theconcave portions, the source electrode 19 is located on the both sidesof the drain electrode 20 to make the channel width become twice, andthus the channel width can be made larger effectively in a small space.

An insulation film 21 is formed so as to cover the source wires 13 andthe TFT 14. Meanwhile, although not shown, the insulation film 21consists of two layers where a lower layer is formed of inorganicinsulation film such as SiN_(x) and an upper layer is formed of organicinsulation film such as photosensitive acrylic resin. Then, countlessconcavity and convexity (not shown) are formed on the organic insulationfilm. The reason why the concavity and convexity are formed on thesurface of the insulation film 21 is to form a pixel electrodereflection type electrochromic display that reflects outside light onthe pixel electrode 15 by using a reflective electrode material made ofmetal for the material of the pixel electrode 15 (described later).

In the case of a general electrochromic display, coloring agent iscontained in the electrolytic layer 80 in order to improve contrast.White particles for coloring are used in the coloring agent, andinorganic particles of calcium oxide, magnesium oxide, titanium dioxideor the like are specifically cited. In using such inorganic particles,they must be mixed into the electrolytic layer 80 at a fixed ratio.Further, in using such electrolytic layer 80, certain thickness of theelectrolytic layer 80 is required because good contrast cannot besecured if the electrolytic layer 80 is made thin too much. Furthermore,when the electrolytic layer 80 is made thinner, there is a danger thatshort circuit will occur between the array-side substrate 10 and thecolor filter-side substrate 50 due to the inorganic particles.

However, since the pixel electrode reflection type electrochromicdisplay does not have the danger of the above-described problem, a gapbetween the array-side substrate 10 and the color filter-side substrate50 can be made narrower. In addition, the size and the application ofthe electrochromic display are often limited in a way to electronicbooks, advertisement on the street, or the like, and an observingposition in such a case is also limited in a way. Therefore, it isbetter to enhance contrast in a specific direction rather than securinga wide view angle by using coloring agent or the like. Consequently, byusing the pixel electrode reflection type electrochromic display inwhich the concavity and convexity are provided on a pixel electrodesurface and a reflecting direction of light is focused in a fixeddirection, contrast in an arbitrary direction can be enhanced. The tiltangle of the concavity and convexity formed on the pixel electrodesurface is set to about 10° in order to focus light in a fixeddirection.

In an area that does not overlap the semiconductor layer 18 of the drainelectrode 20, a contact hole 22 is formed in the insulation film 21.Further, a reflective electrode material made of Al is stacked on theinsulation film 21, the reflective electrode material is patterned bythe photolithography method to form the pixel electrode 15. Ag or Al isspecifically preferable for the reflective electrode material from theviewpoint of reflection efficiency, conductivity, or the like. The drainelectrode 20 of the TFT 14 is connected to the pixel electrode 15 viathe contact hole 22. The surface of the pixel electrode 15 becomesuneven due to the effect of the insulation film 21 located under theelectrode. Further, the area of the pixel electrode 15 is slightlysmaller than the area of one pixel, and a region that can be used fordisplay and a region capable of reflecting light are made wider byincreasing the area of the pixel electrode 15. The end portions of thepixel electrode 15 may be partially overlapped with the gate wire 12 orthe source wire 13 when seen on a plan view as long as they do notcontact an adjacent pixel electrode 15.

Short circuit prevention means for preventing adjacent pixel electrodes15 and adjacent electrochromic layers 30 from short-circuiting with eachother is provided around the pixel electrode 15. It is specifically apartition wall 23 formed so as to surround the pixel electrode 15. Thepartition wall 23 is formed of Novolac resin on the insulation film 21on the gate wires 12 and the source wires 13. Its height isapproximately the same as or higher than the thickness of theelectrochromic layer 30, which is about 3 to 10 μm. For example, whenthe electrochromic layer 30 is formed by screen printing (describedlater), it is preferable that the height of the partition wall beapproximately the same height as the thickness of the electrochromiclayer, and it is desirable that the height of the partition wall behigher than the height of the electrochromic layer 30 when it is formedby a so-called ink jet method. Further, when higher definition displayneeds to be performed, the size of one pixel becomes smaller, a gapbetween pixels becomes narrower, and there is a danger of causing shortcircuit of the pixel electrode 15 with adjacent pixels. Particularly,with advance of even higher definition in future, a distance betweenadjacent pixels, that is, the distance between the pixel electrode 15and the pixel electrode 15 in this case becomes about 5 μm to 30 μm, andthere is a higher chance of causing short circuit.

However, by providing the short circuit prevention means in this manner,short circuit among adjacent pixel electrodes 15 can be prevented, andthe electrochromic layer 30 formed on the pixel electrode 15 isprevented from short-circuiting with an adjacent electrochromic layer30. Note that the partition wall 23 may be any type as long as it is aninsulator, and it may be formed of organic resin or inorganic resinother than Novolac resin. Further, as the short circuit prevention meansother than the partition wall 23, a groove may be formed in theinsulation film 21 at a boundary area to an adjacent pixel, for example.

The electrochromic layer 30 is formed in a region on the pixel electrode15, which is surrounded by the partition wall 23. As the electrochromiclayer 30, one that is made of a material indicating coloring and erasingby electrochemical oxidation or reduction reaction and used in a generalelectrochromic display may be used. For example, tungsten oxide,titanium oxide, molybdenum oxide, iridium oxide, nickel oxide, vanadiumoxide, tin nitride, indium nitride, polythiophene, polypyrrole, metalphthalocyanine, viologen and the like are cited. Alternatively, onehaving a nano-particle thin film state material as described inInternational Publication No. 97/35227 or the like may be used. By usinga nano-particle thin film state material, oxidation-reduction reactioncan be accelerated to increase display response speed or to improvecontrast. The nano-particle thin film state material is used in thisembodiment as well, and a nano-particle thin film made of SnO2 to whichSb is doped is specifically used in this embodiment.

Although the electrochromic layer 30 may be directly formed on the pixelelectrode 15 by a widely known method such as a vacuum evaporationmethod and a sputtering method, for example, nano particles made of SnO₂to which Sb is doped are formed first on each pixel electrode 15 by ascreen printing method in the forming method of the nano-particle thinfilm in this embodiment. Productivity can be improved by the screenprinting method. Further, since the partition wall 23 surrounding theperiphery of the pixel electrode 15 is formed, it is possible to formthe nano-particle thin film highly accurately on the pixel electrode 15by utilizing the partition wall 23. Particularly, when the formingmethod of the nano-particle thin film is done by the screen printingmethod, the height, area or the like of the nano-particle thin film canbe formed very accurately in a space formed by the partition wall 23 onthe pixel electrode 15. Then, after performing a process such assintering the nano-particle thin film and allowing the film to adsorboxidized or reduced compound, the electrochromic layer 30 is formed.

In a color filter-side substrate 50, a color filter 52 providedcorresponding to each pixel, a counter electrode 53, and anelectrochromic layer 54 stacked on the counter electrode 53 are formedon a glass substrate 51.

Black matrix 55 is formed on the glass substrate 51 so as tosectionalize each pixel, and the color filter 52 corresponding to eachpixel is formed at the opening of the black matrix 55. The color filter52 consists of three colors of red (R), green (G) and blue (B), forexample, and one color out of the three colors is arranged correspondingto each pixel. The counter electrode 53 made of ITO or IZO, for example,is stacked on the color filter 52.

The electrochromic layer 54 is formed on the counter electrode 53. Theelectrochromic layer 54 is formed by a layer formed of the nano-particlethin film similar to the array-side substrate 10. A nano-particle thinfilm made of TiO₂ is specifically used in this embodiment. After formingthe nano-particle thin film on the counter electrode 53, theelectrochromic layer 54 is formed after performing a process such assintering the nano-particle thin film or allowing the film to adsorboxidized or reduced compound. Then, the array-side substrate 10 and thecolor filter-side substrate 50 are arranged in a facing manner.

The electrolytic layer 80 serves a role to carry charge by ionscontained in solvent. As the electrolytic layer 80, one used in ageneral electrochromic display may be used, and its constituent materialand forming method are not particularly limited. It also may be a liquidelectrolytic layer, a gel system electrolytic layer, or a solid systemelectrolytic layer.

Solvent into which electrolyte is dissolved can be used as the liquidelectrolytic layer. As specific solvent, water, propylene carbonate,ethylene carbonate, γ-butyrolactone and the like are cited. As specificelectrolyte, sulfuric acid, hydrochloric acid and the like are cited asacids, and sodium hydroxide, potassium hydroxide, lithium hydroxide orthe like is cited as alkalis. As salts, inorganic ion salt, quaternaryammonium salt, cyclic quaternary ammonium salt or the like of alkaline(earth) metal salt such as lithium perchlorate, sodium perchlorate andsilver perchlorate is cited.

As the gel system electrolyte, one produced by mixing and polymerizingacetonitrile, ethylene carbonate, propylene carbonate or their mixturewith polymer such as polyacrylonitrile and polyacrylamide isspecifically cited.

As the solid system electrolyte, polymer side chain such aspolyethyleneoxide having salt such as sulfone imide salt,alkylimidazolium salt and tetra-cyanoquinodimethane salt is cited.

When the electrolytic layer 80 is the liquid electrolytic layer, asealing material is coated on the peripheral portion of the array-sidesubstrate 10 or the color filter-side substrate 50. The sealing materialis coated so as to form an injection port for injecting the material ofthe electrolytic layer 80. Then, the both substrates are bondedtogether, and the material of the electrolytic layer 80 is injected intoa fixed gap generated between the both substrates via the injectionport. Note that the sealing material is coated such that the fixed gapgenerated between the both substrates becomes the layer thickness of theelectrolytic layer 80 (described later). Further, as an injection methodof the material of the electrolytic layer 80, a widely known method suchas a vacuum injection method may be used, for example.

The thickness of the electrolytic layer 80 is between about 5 μm andabout 50 μm, and it is preferably between about 7 μm and about 30 μm. Ifthe thickness of the electrolytic layer 80 becomes too thick, there is adanger that an observer will recognize even the display state of anadjacent pixel through one pixel when he/she observes the display state,so it is preferable that the thickness of the electrolytic layer 80 beas thin as possible. On the contrary, if the thickness of theelectrolytic layer 80 becomes too thin, its role may becomeinsufficient, the array-side substrate 10 may highly likelyshort-circuit with the color filter-side substrate 50 due to a foreignobject, or a problem on manufacturing engineering is considered, so thatthe above-described layer thickness is appropriate.

Although not shown in this embodiment, spherical spacers are sprayed onthe array-side substrate 10. Thus, the thickness of the electrolyticlayer 80 can be maintained at a fixed thickness over the entireelectrochromic display, stable display can be performed, and thespraying can be performed easier than forming columnar spacers on thearray-side substrate 10. Regarding the number of the spherical spacers,it is not necessary to allow spacers to exist in several numbers per onepixel like spherical spacers for strictly controlling a cell gap in aliquid crystal display, for example, but they may be sprayed in onespacer per a plurality of pixels. Therefore, the spherical spacersrarely affect display.

In the electrochromic display, a gate wire drive circuit and a sourcewire drive circuit (both are not shown) for selecting each pixel arerespectively provided at the end portion side of the gate wire 12 andthe end portion side of the source wire 13, and a signal control section(not shown) for controlling the gate wire drive circuit and the sourcewire drive circuit is provided. The gate wire drive circuit controlledby the signal control section applies a gate signal to a predeterminedgate wire 12. The gate signal is applied to the gate electrode 16 of theswitching TFT 14 to turn the TFT 14 to ON state. The source signalapplied to a predetermined source wire 13 is applied from the sourceelectrode 19 of the TFT 14 to the pixel electrode 15 via the drainelectrode 20, and display is performed by a display element 90.

FIG. 4, FIG. 5, FIG. 6, FIG. 7 and FIG. 8 schematically show circuitdiagrams of the electrochromic display in another embodiment. Note thatthe same reference numerals are applied to the same parts as those ofFIG. 3.

FIG. 4, unlike FIG. 3 where display is performed by a voltage drivecircuit, is a display performing display by a current drive circuit. Inaddition to the switching TFT 14, a power supply wire (Vdd) formed alongthe source wire 13 and a TFT 101 for supplying current to the displayelement 90 from the power supply wire (Vdd) are formed in each pixel.The gate electrode, the source electrode and the drain electrode of theTFT 101 are respectively connected to the drain electrode 20 of the TFT14, the power supply wire (Vdd) and the display element 90.

Such current drive circuit can supply larger current to the displayelement 90 than the one in FIG. 3, and oxidation-reduction reaction canbe proceeded at higher speed. In the case of this embodiment, powersupply sorted in two types such as 10V for black display and 0V forwhite display should be performed to the power supply wire (Vdd).Further, a frame rate gradation method is suitable when performinggradation display.

Meanwhile, both the TFT 14 and the TFT 101 are formed of an N-type TFT,that is, a TFT using electrons as carriers, so that a-Si can be used forthe semiconductor layer, and they can be formed in the same process.Further, it is not necessary to form the power supply wire (Vdd) alongthe source wire 13, but may be formed along the gate wire 12, and thepower supply wire may be formed in any direction as long as it cansupply power to each pixel.

FIG. 5 shows the current drive circuit as shown in the above-describedembodiment, where switching means and potential control means areprovided for each pixel. Specifically, an N-type switching TFT 14 isused as the switching means and CMOS 102 made up of a P-type TFT and anN-type TFT is used as the potential control means. The input terminal ofthe CMOS 102 is connected to the drain electrode 20 of the TFT 14, andthe output terminal of the CMOS 102 is connected to the display element90. With this, oxidation-reduction reaction can be proceeded at higherspeed, and gradation display by a voltage gradation method also can beperformed by the potential control means. Meanwhile, since the CMOS 102is used in this embodiment, polysilicon will be used in thesemiconductor layer of the TFT. Accordingly, it exerts effects such thatpower consumption is reduced and peripheral drive circuits can be formedintegrally. Furthermore, the semiconductor layer 18 of the switching TFT14 can be formed by polysilicon as well.

FIG. 6 shows the circuit where the switching means and the potentialcontrol means are provided in each pixel in the same manner as FIG. 5.What is different from FIG. 5 is that it uses two of P-type or N-typeTFTs 103 as the potential control means instead of the CMOS 102 (thefigure shows N-type TFT). Therefore, the semiconductor layer of the TFTscan be manufactured by using a-Si without using polysilicon, and thus aneffect such as easiness of manufacturing is exerted. Since all the TFTsformed for each pixel are N-type TFTs, a-Si may be used in theirsemiconductor layers, so that the increase of manufacturing processescan be suppressed comparing to the case where P-type and N-type TFTs aremixed in each pixel.

FIG. 7 shows a circuit where switching means, rewrite specifying means,potential control means and power source breaking means are provided forthe current drive circuit of the above-described embodiment.Specifically, the switching TFT 14 is used as the switching means, anN-type TFT 104 and a capacitor 105 are used as the rewrite specifyingmeans, CMOS 106 is used as the potential control means, and two N-typeTFTs 107 are used as the power breaking means. The gate electrode of theTFT 104 is connected to a word wire 108 traveling parallelly with thegate wire 12, the source electrode of the TFT 104 is connected to thesource wire 13, and the drain electrode of the TFT 104 is connected tothe capacitor 105 and gate electrodes of the TFTs 107. The sourceelectrodes of the TFTs 107 are severally connected to either one of thetwo power supply wires (Vdd)(Vss). The drain electrodes of the TFTs 107are severally connected to either one of the P-type TFT and N-type TFTwhich constitute the CMOS 106, the input terminal of the CMOS 106 isconnected to the drain electrode 20 of the TFT 14, and the outputterminal of the CMOS 106 is connected to the display element 90.Consequently, in each pixel selected by the word wire 108 and the sourcewire 13, whether or not rewrite is necessary is specified, power issupplied to a pixel specified as one that needs to be rewritten, andpower is not supplied to a pixel specified as one that does not need tobe rewritten.

Since the electrochromic display has a so-called memory capability ofdisplay, if the display of corresponding pixels is the same as the onein the previous pixel selection, power consumption is reduced when suchdisplay is maintained as it is. Consequently, by providing the rewritespecifying means and the power blocking means for each pixel, therewrite specifying means specifies that no rewrite is needed and thepower blocking means blocks supply of power if there is no changebetween the display state in the previous selection and the displaystate of the current selection. The rewrite specifying means specifiesthat rewrite is needed and the power blocking means does not blocksupply of power if there is a change between the display state in theprevious selection and the display state of the current selection. Withthis method, power consumption in the electrochromic display can bereduced. Note that polysilicon will be used in the semiconductor layersof the TFTs because the CMOS 106 is also used in this embodiment.

FIG. 8 shows a current drive circuit where the switching means, therewrite specifying means, the potential control means and the powersource breaking means are provided in each pixel similar to FIG. 7. Whatis different from FIG. 7 is that a P-type or an N-type TFT 109 is usedas the potential control means instead of the CMOS 106 (the figure showsN-type). Therefore, the semiconductor layer of the TFTs can bemanufactured by using a-Si without using polysilicon, and thus an effectsuch as easiness of manufacturing is exerted. Since all the TFTs formedfor each pixel are N-type TFTs, a-Si may be used in their semiconductorlayers, so that the increase of manufacturing processes can besuppressed comparing to the case where P-type and N-type TFTs are mixedin each pixel.

Meanwhile, the power supply wires (Vdd)(Vss) are shown in the circuitdiagrams shown in FIG. 4 to FIG. 8, and the end portions of the powersupply wires are connected to the power source. In this case, there is adanger that power supply capability will reduce as they become furtherfrom the power source due to wiring resistance. Therefore, the both endsof the power supply wire may be connected to the power source oradjacent power supply wires are connected to each other via one or moreconnection points to prevent the power supply capability from beingreduced. In such a case, when the connection points are formed in aladder shape, power can be supplied even if one wire out of the powersupply wires is broken.

Note that other modes than the above-described embodiments within therange of the gist of the present invention can be realized. For example,other insulative substrates such as a plastic substrate may be usedother than the glass substrate 11. Furthermore, the insulative substratemay be film state having flexibility.

Due to the short-circuit prevention means provided around the pixelelectrode, short-circuit between pixel electrodes or short-circuitbetween electrochromic layers does not occur between adjacent pixels,and thus an electrochromic display capable of performing higherprecision can be provided.

1. An electrochromic display comprising: a plurality of pixels, whereinthe plurality of pixels includes a first pixel comprising: a pixelelectrode; a counter electrode; an electrochromic layer disposed betweenthe pixel electrode and the counter electrode; and a partition wallsurrounding a periphery of the pixel electrode, wherein the partitionwall is configured to prevent a short circuit between the first pixeland a second pixel from the plurality of pixels, and wherein thepartition wall is formed on an insulation film which is adjacent to thepixel electrode.
 2. A pixel for use in an electrochromic display, thepixel comprising: a pixel electrode; a counter electrode; anelectrochromic layer disposed between the pixel electrode and thecounter electrode; an electrolytic layer disposed between the pixelelectrode and the counter electrode; and a partition wall surroundingthe pixel electrode, wherein the partition wall is configured toinsulate the pixel electrode from an adjacent pixel electrode, andwherein the partition wall is formed on an insulation film which isadjacent to the pixel electrode.
 3. The pixel of claim 2, wherein theelectrochromic layer comprises a nano-particle thin film.
 4. The pixelof claim 3, wherein the nano-particle thin film is mounted on the pixelelectrode in an area formed by the partition wall.
 5. The pixel of claim4, wherein the nano-particle thin film is formed in the area using ascreen-printing method.
 6. The pixel of claim 2, wherein theelectrochromic layer has a thickness of 3 μm to 10 μm.
 7. The pixel ofclaim 2, wherein an upper surface of the partition wall is even with atop surface of the electrochromic layer.
 8. The pixel of claim 2,wherein the electrolytic layer has a thickness of 5 μm to 50 μm.
 9. Thepixel of claim 2, wherein the electrolytic layer comprises sphericalspacers.
 10. The electrochromic display of claim 1, further comprisingan electrolytic layer disposed between the pixel electrode and thecounter electrode.
 11. The electrochromic display of claim 1, whereinthe partition wall has a height equal to or greater than a thickness ofthe electrochromic layer.
 12. The electrochromic display of claim 1,wherein the partition wall surrounds at least a portion of a secondperiphery of the electrochromic layer to prevent short circuitingbetween the electrochromic layer and a second electrochromic layer ofthe second pixel.
 13. The electrochromic display of claim 1, wherein thesecond pixel includes a second pixel electrode, and wherein a distancebetween the pixel electrode and the second pixel electrode is between 5um and 30 um.
 14. The electrochromic display of claim 1, wherein thepartition wall comprises at least one of an organic resin or aninorganic resin.
 15. The electrochromic display of claim 1, wherein thepartition wall comprises a novolac resin.
 16. A method for creating apixel of an electrochromic display, the method comprising: forming apixel electrode; forming a counter electrode; forming a partition wallbetween the pixel electrode and the counter electrode, wherein thepartition wall surrounds the pixel electrode and is configured toinsulate the pixel electrode from an adjacent pixel electrode, andwherein the partition wall is formed on an insulation film which isadjacent to the pixel electrode; and forming an electrochromic layerbetween the pixel electrode and the counter electrode, wherein theelectrochromic layer is surrounded, at least in part, by the partitionwall.
 17. The method of claim 16, wherein the electrochromic layercomprises a nano-particle thin film, and further comprising using ascreen printing method to form the nano-particle thin film in an areaformed by the partition wall.
 18. The method of claim 17, wherein thenano-particle thin film comprises tin oxide doped with antimony.
 19. Themethod of claim 16, further comprising forming an insulation filmadjacent to at least a portion of the pixel electrode, wherein thepartition wall is formed on the insulation film.
 20. The electrochromicdisplay of claim 1, further comprising an electrolytic layer disposedbetween the pixel electrode and the counter electrode, wherein thepartition wall consists of materials other than an electrolytic layer.21. The method of claim 16, further comprising forming an electrolyticlayer between the pixel electrode and the counter electrode, whereinpartition wall consists of materials other than the electrolytic layer.